In high-speed machinery with shafts rotating at elevated velocities, e.g. of 200,000 RPM, journal bearings supporting these shafts must operate with great precision and minimum wear. Various tests have therefore been devised for checking the components of such bearings, especially the rotary bodies thereof, in order to facilitate selection of only those whose dimensions and other structural parameters conform within narrow tolerances to predetermined standards. Such tests and equipment suitable therefor have been described in an article by W. Kirchner entitled Das Messen und Sortieren von Walzkorpern fur Prazisionswalzlager, first published in the magazine "TZ fur praktische Metallbearbeitung", vol. 58 (1964), No. 12, pages 679-684, by Technischer Verlag Gunter Grossmann GmbH, Stuttgart-Vaihingen, German Federal Republic, and reprinted in Publication No. 52,102 of Kugelfischer Georg Schafer & Co., the assignee of my present invention.
Despite scrupulous administration of these tests and elimination of rejects incapable of correction by further machining, certain rollers used in high-speed bearings were found to show unexpected wear in the region of their end faces which at first could not be explained. I have found the cause to reside in an eccentricity of the center of gravity of the roller body which gives rise to an unbalance tending to tilt the axis of that body relatively to its axis of rotation within the bearing. If the eccentricity is due to single surface irregularity, the defect can be detected by conventional methods. In many instances, however, the unbalance is the result of a multiplicity of minor deviations, not readily ascertainable by themselves, from exact cylindricity or conicity, parallelism of end faces and other prerequisites. Internal cavities and other structural inhomogeneities below the surface also defy detection.